Image intensifier including matrix of elongated electrodes for locating output signals geometrically

ABSTRACT

A particle detector system comprising a channel image intensifier having a planar output electrode subdivided into an array of parallel electrode conductors with each conductor connected to a separate terminal, an array of parallel target conductors lying in a plane parallel to the electrode conductors on the output side of the device and orientated perpendicular to the electrode conductors, and a second set of terminals each of which is associated with one of the target conductors. The target conductors may be associated with luminescent elements to generate a two-dimensional visual display.

United States Patent lnventor Brian William Manley Burgess Hill, Sussex,England Appl. No. 743,764 I Filed July 10, 1968 Patented Jan. 5, 1971Assignee U.S. Philips Corporation New York,N.Y. a corporation ofDelaware. by mesne assignments Priority July 12, 1967 Great Britain No.32016/67 IMAGE INTENSIFIER INCLUDING MATRIX OF ELONGATED ELECTRODES FORLOCATING OUTPUT SIGNALS GEOMETRICALLY 5 Claims, 5 Drawing Figs.

U.S. Cl 250/209, 178/76; 250/213, 250/220; 313/96 Int. Cl H01j 39/12Field of Search 250/83.3, 213, 209, 220; 178/76, 7.1; 340/173; 313/96,97,

[56] References Cited UNITED STATES PATENTS 2,892,968 6/1959 Kallmann eta1 178/7.6X 3,121,861 2/1964 Alexander 250/213X 3,449,582 6/1969Sackinger 250/213V.T.

Primary Examiner-James W. Lawrence Assistant Examiner- C. M. LeedomAttorney-Frank R. Trifari ABSTRACT: A particle detector systemcomprising a channel image intensifier having a planar output electrodesubdivided into an array of parallel electrode conductors with eachconductor connected to a separate terminal, an array of parallel targetconductors lying in a plane parallel to the electrode conductors on theoutput side of the device and orientated perpendicular to the electrodeconductors, and a second set of terminals each of which is associatedwith one of the target conductors. The target conductors may beassociated with luminescent elements to generate a two-dimensionalvisual display.

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INVENTOR. BRIAN w. MANLEY AGENT PATENTEU m SHEET 3 0F 3 INVENTOR, BRIANw. MANLEY AGEN IMAGE INTENSIFIER INCLUDING MATRIX F ELONGATED ELECTRODESFOR LOCATING OUTPUT SIGNALS GEOMETRICALLY This invention relates toelectronic image intensifier devices. More particularly the inventionrelates to channel intensifier devices and to electronic imaging tubesemploying such devices. Such devices are secondary-emissiveelectronrnultiplier devices comprising a matrix in the form of a platehaving a large number of elongated channels passing through in thedirection of, its thickness, and both sides of the matrix separated byits thickness are covered by conductive layers which act respectively asinput and output electrodes Such intensifier devices are well known andwhen incorporated in electronic imaging tubes, a potential difference isapplied between the two electrode layers of the matrix so as to set upan electric field which establishes a potential gradient along thechannels created by current flowing through the bulk material of thematrix or if such material has a very high resistance through resistivesurfaces fonned inside the channels. Secondary-emissive multiplicationtakes place in the channels and the output electrons may be acted uponby a further accelerating field which may be set up between the outputelectrode and a suitable target, for example a luminescent displayscreen. a v

It is an object of the present invention to employ a channel intensifierdevice for detecting particles or radiation quanta and determining thedistribution thereof over a given area. Such distribution may, in somecases, be sufficiently complex to represent a crude form of imaging inwhich the definition and the number of picture elements are very low ascompared with imaging applications of the broadcast television type. Theinvention is also applicable in cases where, from a low particle rate(defined below) a picture of fairly high definition can be built upgradually with the aid of additional storage means, for example gammaradiography for medical purposes.

The invention provides a particle or radiation quantum detector systemcomprising a channel intensifier device as defined above wherein theoutput electrode is substantially planar and is subdivided into an arrayof parallel electrode conductors with each conductor connected to aseparate terminal, an array of target conductors lying substantially ina plane parallel to the plane of said electrode conductors on the outputside of said device which target conductors are parallel to each otherand orientated at, or approximately at right angles to the direction ofthe electrode conductors, and a second set of terminals each of whichappertains to one of said target conductors.

In such an arrangement the array of electrode conductors replaces themore normal form of output electrode which is usually (but not always)described as a single electrically continuous layer. Similarly, thepresent array of target conductors replaces the continuous conductivetarget layer which is more usually provided on a phosphor screen on theoutput side of a channel intensifier device.

p A particle or radiation quantum detector system according to theinvention can be combined with an output circuit arrangement comprisinga separate charge detector for each electrode conductor and a separatecharge detector for each target conductor, and means whereby each eventcauses a simultaneous response in one of the electrode detectors and inone of the target detectors so as to provide, together a coordinateposition for the event. This mode of operation is suitable forapplications in which there is a low particle or quantum rate, i.e.,there are so few events that the chance of two simultaneous events canbe ignored. If the rate is higher, means can be provided (as will bedescribed) to inhibit the system when ambiguities arise as to the numberand position of events for example, two simultaneous events which arespaced apart in both the X and the Y directions will identify four(instead of two) electrode intersections between two electrodeconductors and two target conductors (it is convenient to use the termintersection" even though the two arrays of conductors are spacedapart.)

In addition to the individual charge detectors it may in some cases bedesirable to provide one general discriminator either in a common supplycircuit of the target detectors or in that of the electrode detectorsfor purposes such as determining whether the magnitude of an event :isgreater or smaller than a given datum.

The target conductors may or may not be associated with luminescentelements to provide a two-dimensional visual display of the positions ofdetected particles in addition to the counting and/or recording actionof the circuit actuated by the output signals. If this is done, theluminescent elements may or may not form a continuous phosphor screenand they may be provided on the side of the target array remote from thechannel plate (if so, the array can be in the form of aluminum backingstrips).

Embodiments of the invention will now be described by way of examplewith reference to the drawing in which:

FIG. 1 shows schematically a system according to the present inventionarranged within an evacuated envelope;

FIG. 2 shows a detail of the output surface of the matrix;

FIG. 3 shows schematically part of a more complete arrangement;

FIG. 4 shows the arrangement completed with a cathode ray tube; and

FIG. 5 shows a schematic representation of the electric circuit.

The envelope comprises a channel intensifier device I together with atarget system TaTn. The channel intensifier device 1 includes an inputelectrode El covering its input face and an output electrode composed ofan array of parallel electrode conductors in the form of strips E2a,E2b-E2n. Each of the latter is connected through a separate chargedetector or amplifier to a common supply source Bl. For simplicity allthese electrode detectors are shown as a combined electrode detectorsystem ED.

In some applications input radiation can be imaged on to the device I byan optical system and the system may require a photocathode on the inputside of the channel plate I either in contact therewith or spacedtherefrom as described in prior specifications.

By contrast, in diagnostic X-ray radiography or gamma-rayautoradiography it may not be necessary to use a photocathode sincegamma or X-ray photons can cause electron emission from the material ofthe matrix which is usually made of a suitable glass or combination ofglasses. Moreover, optical systems are not used in these applicationsand for this reason the body to be examined is usually placed as closeto the channel intensifier device as is practicable, and this isindicated schematically at B. As an example of this, in the case ofgamma-ray radiography, the body B which is to be examined can be placedas close as possible to the device I and I emits a pattern ofgamma'radiation via a lead matrix collimator (not shown) on to the inputface of the device I. Whenever a gamma particle enters the material ofthe channel plate, one or more electrons may be produced and may escapeinto a channel. Then electron multiplication can take place in themanner well known. A pulse of secondary electrons will emerge from theoutput end of the said channel and in so doing will provide an outputsignal in the detector corresponding to the particular electrode strip.

FIG. 1 can also be taken as illustrating the case in which the inputradiation is constituted by X-rays irradiating the body B from a pointsource (not shown). In conclusion, FIG. 1 can be taken as illustratingboth this case and also the use of gamma rays directed from the body Bto the channel plate via a lead collimator.

The target is constituted by a set of parallel target conductors Ta, Tb--Tnwhich lie in a direction which is at, or approximately at, rightangles to the direction of the electrode strips, for example in avertical direction if the electrode strips E2a, E2b,E2n are horizontal.These target conductors are also each connected to a separate chargedetector or amplifier, but said detectors are all shown for simplicityas a combined target detector system TD connected to a common source ofaccelerating potential B2.

Although it is not essential to have an extremely regular disposition ofthe channels in the channel plate nor to have an extremely accurateregistration between individual output electrode conductors and theindividual channels, it is possible to have one row of channelscorresponding to each one of the electrode strips-as shown in FIG. 2.Alternatively it is possible to have more than one row of channelscorresponding to one electrode strip, or just a statistically uniformband of channels covered by each electrode strip if the channelstructure is materially finer than the desired resolution.

The arrangement of FIGS. 1 and 2 is shown more clearly in FIG. 3 where,for the sake of clarity, only a very small number of electrodeconductors and target conductors is shown, namely four of each. As willbe seen, each of the electrode conductors is a strip E2a-E2d connectedthrough a separate charge detector EDa-EDd. Similarly each of the targetconductors Ta-Tdis a strip connected through a separate charge detectorTDa-TDd. If a particle enters a particular channel Cx it will cause anoutput of secondary electrons as shown and it will also cause an outputsignal in the electrode detector EDa and also an output signal in thetarget detector TDc. These two signals, if collated will give theposition of the event in channel Cx as a pair of coordinates.

This collation can be carried out e.g. with the aid of a ferrite corestore which can be used as the source of information from which a C.R.T.display can be generated.

Alternatively the collated coordinate information can be directly fed toa cathode-ray storage tube in order to build up therein and display theinformation.

Both these arrangements are illustrated schematically in FIG. 4 wherethe unit M may be a ferrite core store with readout means connected to aconventional C.R.T. display tube. For the alternative arrangement, theunit M can be a ferrite core matrix used only for collation while theCRT is a display tube of the storage type.

A circuit arrangement shown in greater detail, in FIG. 5 includesinhibiting means of the kind referred to previously.

Thecharge detectors are constituted by the stages of two shiftregisters. When a pulse of charge is registered on both horizontal andvertical arrays, a digit is stored in each shift register in the stagescorresponding to the row position and column position of the event. Thereadout process then entails the shifting of the contents of theregisters to the right in such manner as to simulate line and framescanning. Thus in each register position of the column register, it isnecessary to cycle completely the row register. Therefore the shiftpulses to the column register occur with a frequency a factor n lowerthan the row shift pulses (i n is equal to the number of rows) and thecycling continues until the stored digits appear at the right hand endof the registers at the same instant. A bright-up pulse is then producedon the writing beam control of an integrating storage display tube whichis being scanned in synchronism with the register shifts. In detail, theoperation is as follows.

Charge emerging from a channel and striking a target (or column) stripwill produce a pulse of charge in that strip and also in the electrode(or row) strip containing the channel. These pulses will be similar inmagnitude but opposite in sign since one is due to electrons leaving andthe other is due to electrons arriving. The purpose of exclusive OR 1and exclusive OR 2 is to ensure that there is only one pulse of chargefrom the rows and one from the columns. In the event of there beingeither no pulse from one of the sets of strips, or more than one fromone or both sets, AND gate 3 produces no output and AND gate 4 does notproduce a start pulse. Thus the unwanted signal is ignored. This is toguard against spurious events and to inhibit the system against twosimultaneous events which the system cannot analyze unambiguously.

In the event that there is only one row pulse and one column pulse, theanalysis proceeds as follows. The column pulse produces a pulse fromexclusive ORgate 5 which results in a start ulse from AND gate 4. Thispulse acts via unit 6 (a J-K fhpop) to open the switch 7 so preventingfurther pulses (arriving during the analysis of the present pulse) fromproducing disturbing signals. The start pulse is also'fed into AND gate8 and thereby results in a sequence of clock pulses to the shiftregisters, so cycling them until each produces an output pulse into ANDgate 9, when a bright-up gating pulse is producedon the writing gun ofthe storage c.r.t. In addition, a stop pulse goes to the unit 6, sostopping the register cycling process and clearing the registers, andclosing the switch 7 to await the next signal pulse (flip-flop 6 is ofthe known bistable J-K type having always 0 at one output and 1" at itsother output, these outputs being reversed when the unit changes state).

The synchronized operation of the scan generator is ensured by aframe-trigger and line sync (FL) unit 11 which is controlled by clockpulses which have been divided by-n in the divider unit 10.

In space applications it may not be desirable to have an evacuatedenvelope for the channel plate and target system as shown in FIG. 1, andtherefore the electrode and target conductor terminals, referred tothroughout this Specification, may be circuit connections or connectorsrather than terminals formed in the wall ofa tube.

Iclaim: t

l. A particle or radiation quantum detector system comprising a channelintensifier device comprising input and output electrodes separated byan insulating matrix having elongated channels therein extending betweensaid input and output electrodes, the walls of said channels beingsecondary emissive, said output electrode being substantially planar andbeing subdivided into an array of parallel electrode conductors witheach conductor connected to a separate terminal, an array of targetconductors lying substantially in a plane parallel to the plane of saidelectrode conductors on the output side of said device which targetconductors are parallel to each other and orientated at, orapproximately at, right angles to the direction of the electrodeconductors, and a second set of terminals each of which appertains toone of said target conductors.

2. A detector system as claimed in claim 1 contained in an evacuatedenvelope and wherein the electrode conductor terminals and the targetconductor terminals are secured on said envelope.

3. A detector system as claimed in claim 2 wherein the target conductorsare associated with luminescent elements to provide a two-dimensionalvisual display of the positions of detected particles.

4. A detector system as claimed in claim 1 wherein an output circuitarrangement comprises a separate charge detector for each electrodeconductor and a separate detector for each target conductor, and meanswhereby each event causes a simultaneous response in one of theelectrode detectors and in one of the target detectors so as to provide,together, a coordinate position for the event.

5. A combination as claimed in claim 4 including means for..

1. A particle or radiation quantum detector system comprising a channelintensifier device comprising input and output electrodes separated byan insulating matrix having elongated channels therein extending betweensaid input and output electrodes, the walls of said channels beingsecondary emissive, said output electrode being substantially planar andbeing subdivided into an array of parallel electrode conductors witheach conductor connected to a separate terminal, an array of targetconductors lying substantially in a plane parallel to the plane Of saidelectrode conductors on the output side of said device which targetconductors are parallel to each other and orientated at, orapproximately at, right angles to the direction of the electrodeconductors, and a second set of terminals each of which appertains toone of said target conductors.
 2. A detector system as claimed in claim1 contained in an evacuated envelope and wherein the electrode conductorterminals and the target conductor terminals are secured on saidenvelope.
 3. A detector system as claimed in claim 2 wherein the targetconductors are associated with luminescent elements to provide atwo-dimensional visual display of the positions of detected particles.4. A detector system as claimed in claim 1 wherein an output circuitarrangement comprises a separate charge detector for each electrodeconductor and a separate detector for each target conductor, and meanswhereby each event causes a simultaneous response in one of theelectrode detectors and in one of the target detectors so as to provide,together, a coordinate position for the event.
 5. A combination asclaimed in claim 4 including means for inhibiting the system whenevertwo or more events occur simultaneously at different coordinatepositions.